Design of Terahertz SIS Mixers Using Nb/AlN/Nb Junctions Integrated With All-NbTiN Tuning Circuits
Design of Terahertz SIS Mixers Using Nb/AlN/Nb Junctions Integrated With All-NbTiN Tuning Circuits
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DOI：
10.1109/tasc.2016.2632628
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发表时间：
2017-06
影响因子：
1.8
通讯作者：
Y. Uzawa;M. Kroug;T. Kojima;K. Makise;Álvaro González;S. Saito;Y. Fujii;K. Kaneko;H. Terai;Zhen Wang
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文献类型：
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作者：
Y. Uzawa;M. Kroug;T. Kojima;K. Makise;Álvaro González;S. Saito;Y. Fujii;K. Kaneko;H. Terai;Zhen Wang
我们已经设计了超导体-绝缘体-超导体（SIS）混频器使用Nb/AlN/Nb隧道结集成NbTiN/SiO2/NbTiN微带调谐电路的阿塔卡马大毫米/亚毫米阵列（阿尔马）波段10（0.78-0.95太赫兹）。为了设计调谐电路，我们使用太赫兹时域光谱实验推导出的复电导率的相对较厚的NbTiN薄膜沉积在石英基板上直接作为接地平面和RF溅射SiO2作为微带。结果表明，这两种薄膜的电导率可以用修正的Mattis-Barclay理论来描述。我们还研究了结加热效应源于准粒子捕获在Nb电极嵌入NbTiN电路通过改变电极的体积。结果表明，与具有薄（~50 nm）电极的Nb/AlN/Nb隧道结相比，具有厚（~200 nm）对电极的Nb/AlN/Nb隧道结的电流-电压曲线显示出更高的间隙电压和更小的回弯。利用这些发现，我们设计的SIS混频器采用Nb/AlN/Nb结，电流密度为15 kA/cm ~ 2和所有NbTiN调谐电路可以覆盖带10具有良好的灵敏度。
We have designed superconductor-insulator-superconductor (SIS) mixers using Nb/AlN/Nb tunnel junctions integrated with NbTiN/SiO2/NbTiN microstrip tuning circuits for the Atacama Large Millimeter/submillimeter Array (ALMA) Band 10 (0.78-0.95 THz). In order to design the tuning circuits, we used terahertz time domain spectroscopy to experimentally derive the complex conductivity of relatively thick NbTiN films deposited on quartz substrate directly as a ground plane and on RF-sputtered SiO2 as a microstrip. Results showed that the conductivities of both films can be described by a modified Mattis-Bardeen theory. We also investigated the junction heating effects originating from quasi-particle trapping in the Nb electrodes embedded in NbTiN circuits by varying the volume of the electrodes. It was confirmed that current-voltage curves of Nb/AlN/Nb tunnel junctions with thick (~200 nm) counter electrodes contacting NbTiN wirings showed higher gap voltages as well as reduced back-bending than those with thin (~50 nm) electrodes. Making use of these findings, our designed SIS mixers employing Nb/AlN/Nb junctions with a current density of 15 kA/cm2 and all-NbTiN tuning circuits may cover the Band 10 with good sensitivity.